Introduction to Spacecraft (2024-2025) PDF

Introduction to Spacecraft Unit 1: Introduction to Spacecraft Master in Aeronautical Engineering Escuela Técnica Superior de Ingeniería Universidad de Sevilla Academic Year 202...

Introduction to Spacecraft Unit 1: Introduction to Spacecraft Master in Aeronautical Engineering Escuela Técnica Superior de Ingeniería Universidad de Sevilla Academic Year 2024-2025 Spacecraft Systems Unit 1 A. Franco 1 / 12 Unit 1: Introduction to Spacecraft Introduction. The space environment Spacecraft systems System design process Spacecraft Systems Unit 1 A. Franco 2 / 12 Introduction I Spacecraft design? We need to see the bigger picture Project/Programme/System Earth segment Launch segment Space segment (spacecraft) Spacecraft Systems Unit 1 A. Franco 3 / 12 Introduction II Earth segment Earth stations network Transmission of instructions to the spacecraft (command). Data receiving by the spacecraft (telemetry). Following the spacecraft position (tracking). Mission control centre Spacecraft monitoring and control in real time. Estimation and prediction of spacecraft orbit and attitude. Planning of future operations. Analysis of received data. Launch segment Launch complex. Launch vehicle. Space segment Platform: Divided into functional subsystems. Payload. Spacecraft Systems Unit 1 A. Franco 4 / 12 The space environment I The spacecraft desgin strongly depends on the particular mission considered. However, all designs share common characteristics that enable the operation within a utterly hostile environment: The space environment. Space environment features: Space vacuum Thermal environment Space radiation Microgravity Micrometeoroids Space debris Spacecraft Systems Unit 1 A. Franco 5 / 12 The space environment II Space vacuum Residual atmosphere at low Earth orbits Need for propulsion. Aerobraking and aerocapture menoeuvres are possible. In combination with thermal cycles, it alters thermo-optical properties (reflexion/emission). It induces degassing, thus changing physical properties. Metals release interstitial gases. Polymers lose volatile component (may be an important mass fraction). Hygroscopic materials release water that can condense somewhere. Thermal environment In vaccum, the only mechanism for heat transfer is radiation. The source (Sun) and the sink (space background) impose large temperature gradients: A careful thermomechanical design is needed. Spacecraft Systems Unit 1 A. Franco 6 / 12 The space environment III Space radiation Types: EM radiation from the sun, solar particles (solar wind), and galactic cosmic rays. Effects on electronic systems on board: Semiconductors altering. Local ionizing leading to integrated circuits failure. Noty important in sufficiently low Earth orbits. Microgravity: Weightlessness is only partial, and gravity gradient is active. Pros: Ligther structures and scientific research possibilities. Cons: More difficult processes involving fluids and negative effects on human health. Spacecraft Systems Unit 1 A. Franco 7 / 12 The space environment IV Micrometeoroids Not so dangerous (particles of around 1 µm are shielded by an Al foil of 0,5 mm thick). In some missions, the structure and the thermal insulator provide enough shielding against them. Long missions may require additional protection. In pressurised tanks, their continued impact can lead to failure due to stress concentration. Space debris Anthropogenic particles: Astonishing figures. 40500 δ ≥ 10 cm, 1.1 million 1 cm − 10 cm, 130 million 1 mm − 1 cm. Space Surveillance Networks catalogue: 36900 objects. Higher densities are found at medium Earth altitudes (800 – 1000 km) and near 1400 km. Unexpected impact can have catastrophic consequences (e.g.: against radiators or space suits). Spacecraft Systems Unit 1 A. Franco 8 / 12 Spacecraft systems I Structure and mechanisms system Attitude determination and control system Power system Thermal control system Environmental control system Telemetry, command, and data management system Propulsion system Spacecraft Systems Unit 1 A. Franco 9 / 12 Spacecraft systems II Structure and mechanisms system The structure is the skeleton that bears all the equipment and stands the mechanical loads. It must be light but strong: Al, Mg, Be, Composites. Due to the volume constraints that the launch vehicles impose to the spacecraft, some of them are launched in a retracted configuration and subsequently deployed in orbit. Attitude determination and control system Attitude control is the process of orienting the spacecraft to a given direction. It includes: Attitude stabilising: typically through gyroscopic stabilisation (or spin stabilisation) and three-axis stabilisation. Control menoeuvres: They rely upon sensors (optical sensors, gyroscopic sensors) and actuators (reaction wheels, flywheels, and paired thrusters). Spacecraft Systems Unit 1 A. Franco 10 / 12 Spacecraft systems III Power system It carries out the generation, storage, distribution and control of the electrical power needed to operate the spacecraft. Subtasks: Generation: Photovoltaic (Pe ≤ 25 kW), thermosolar, nuclear. Storage: Electrochemical batteries (Ni-Cd, Ni-H, Li ion). Distribution: 28 V DC, 50 V DC, 100/120 V DC, or 300 V DC. Thermal control system It keeps the temperature of the spacecraft and its equipment within the operational envelope with the least energy consumption. Thermal radiation is the main effect. Solutions: Small spacecraft: Coatings, surface finishing, MLI blankets. Large spacecraft: All the previous plus fluid loops to trabnsfer the heat emitted by equipment to the radiators. It includes the Thermal Protection System, which acts at the reentry to planets with atmosphere. Spacecraft Systems Unit 1 A. Franco 11 / 12 Spacecraft systems IV Environmental control system It provides a life-compatible environment in manned missions. Telemetry, command, and data management system It allows uplink and downlink between spacecraft and Earth stations. It decodes and distributes the received information, as well as gathers and encondes the information to be sent. Propulsion system It satisfies the need for generating a force and, ultimately, an impulse related to the menoeuvres to change the orbit or control the attitude and the orbit. Spacecraft Systems Unit 1 A. Franco 12 / 12